Automatic sheet feeding mechanism



Jan. 12, 1954 E. L. JOHNSON AUTOMATIC SHEET FEEDING MECHANISM 2Sheets-Sheet 1 Filed April 25, 1951 Jan. 12, 1954 AUTOMATIC SHEETFEEDING MECHANISM Filed April 25, 1951 :2 Shfts-Shet 2 tor.- E'Zmer ZZ.Jbiznso'n Mtty.

E. L. JOHNSON 2,665, 06

Patented Jan. 12,1954

2,665,906 AUTOMATIC SHEET FEEDING MECHANISM Elmer L. Johnson, Chicago,111., assignor to Bell & Howell Company, Chicago, 11],, a corporation.

of Illinois Application-April '25, 195-1-,seria1No. 222,866 14' claims.(or. 271 s6) My invention relates particularly to-automatic sheetfeeding mechanism for use ona microfilm recorder embodying sheethandling or feeding mechanism provided with a horizon-tally drivenrotatable sheet feed drum to which sheets are sequentially fed, althoughnot limited to this use alone, and particularly concerns a feeder of thetype described and claimed in my U. applications for Letters Patent,Serial No. 53,646, filed Gctober 9, 1948, now Patent No. 2,652,248, andSerial No. 147,498, filed March 3, 1950, now Patout No. 2,626,148,and-U1 53'. application for Letters Patent of Malcolm G. Townsley,Serial No. 151,751, filed March 24, 1950, now Patent No. 2,655,3 l4, allfor improvement in Automatic Sheet Feeding Mechanism, onwhich thisinvention'may be considered an improvement.

Objects of the invention reside in the provision in an automatic sheetfeeding mechanism of a novel, simple, compact andelicctive means forpreventing, at least to a large extent, the undesired feeding ofsuperposed sheets instead of single sheets, which is well adapted forfeeders of the above type, and which is preferably -convenientlyadjustal'ole for maximumfunctioning under various conditions,

Ihe invention will lie-more readily understood by'rei'erence to theaccompanying drawing forming apart hereof and in which-s Figure 1 is aside elevation of an automatic v Figure 2 is a front elevation of saidfeeding mechanism and also showing it in mounted association with partsof a microfilm recorder;

Figure 3 is a partial sectional view taken substantially on the line 3-4of Figure 1;

Figures 4 and 5 are partial sectional views taken similarly to Figure land showing different conditions of operation;

Figure 6 is a partial sectional view taken substantially on the line-6-6 of Figure 2;

Figure *l is a partial bottom plan view of the feeding mechanism withparts broken away and shown in section; and Figure- 8 is a partialsection taken substantially on the line 88 of- Figure 7.\

Referring to the drawing and particularly Figures 1, 2 and 6, the sheethandling machineon which the automatic sheet feeding mechanism embodyingmy invention is shown to be used, is a microfilm recorder which includesa horizontal rotatable sheet feed drum which is driven in a clockwisedirection in Figures 1, and; 6, a generally horizontal stationary handsheet feed plate or chute 2- inclined downwardly toward the upperportion of the feed drum: in tangential sheet feeding relation therewithfor the sequential hand feeding of sheets to the feed. drum which incooperation with pressure rollers, not shown, feeds the sheetsdownwardlyfor the photographing of the sheets by the recorder, and. a drivinggear-'3 secured at one end of the feed for rotation therewith and:disposed in concentric relation with and having its pitch diameterthesame as that of the feed drum.

The automatic sheet feeding. mechanism em bod'ying my inventioncomprises as follows:

A rectangular support-plate dis provided: with upwardly extendingbearing brackets at opposite sides of the front end thereof, of whichone, designated 5 in Figures- 2 andfi, comprises an upturned: portion orthe supportp-Iate, and of which the-*o'ther, designated at it in Figures1., 2 and 3, comprises a separate bracket secured. downwardly on thesupport plate. A rotatable shaft '1' isarranged transversely or". andabove the support plate atsaidend thereon see Figure 2, and is iournaledat one end thereof on the bracket' d, as designated at 8 in Figure 2,and is journals-d adjacent the other end thereof on the bracket c, asdesignated at '9 in Figure 3. A drum en-gaging roller I I, disposedadjacent and on the outside of the bracket 6, is rotatably mounted onthe shaft? as designated at 12, this roller bein'g'of relativelylargediameter and projecting below the support late for rolling'ensgagement downwardly on the feed drum I.

Two support legs I3, see Figures 1 and 2; are spaced transversely of thesupport plate l and are formed integrally therewith and extend down,-wardly therefrom in the region-oi the rear end thereof, and reducedshoulder iorming lower end portions Id thereof are loosely engageable inapertures I 5 through the portion of the teed plate 2 remote from thefeed drum I and thus provide a pivotal: mounting for thesupport plate 7on an axis parallel to and horizontally spaced from the feed drum. Thesesupport legs coopcrate with the roller H in its rolling engagem'entdownwardly on the feed drum I and with a downwardly projecting supportleg [6, on and formed integrally with the support plate in the region ofthe shaft 1 and at the side of the support plate opposite that at whichthe roller II is disposed and bearing downwardly on the feed plate 2",to position the support plate above the feed plate and inclineddownwardly toward the upper portion of the feed drum in tangential sheetfeeding relation therewith.

The drum engaging roller I I is disposed to engage the feed drum Iadjacent the driving gear 3 of the feed drum, and is provided at theouter side thereof with a driven gear I! which is fixed with this rollerfor rotation therewith and is disposed concentric thereto and has itspitch diameter the same as the diameter of the drum engaging roller, seeFigures 1 and 3 so that when the roller Ii is engaged downwardly on thefeed drum, the driven gear II is downwardly engaged in proper mesh withthe feed drum drive gear 3 for driving the driven gear and its rollerfrom the drive gear and feed drum in a positive manner, the weight ofthe feeding mechanism tending to maintain the roller II and driven gearI] in engagement with the feed drum I and drive gear 3.

The support plate 4 forms the base of the automatic feeding mechanismand carries the mechanism thereof including the drum engaging roller II,the driven gear I1 and the shaft I as a unit, so that the automaticfeeding mechanism is conveniently portable and is readily installed onand removed from the sheet handling machine by engaging and disengagingthe legs I3 with the apertures I5 with vertical movement of the feedingmechanism.

Two axially spaced bored friction feed rolls l8, see particularlyFigures 2 and 6, are rotatably mounted on the shaft I between thebearing brackets 5 and 6, they being surfaced with a friction material,such as soft rubber and being of smaller diameter than the drum engagingroller I I and arranged above the support plate 4 in approximatelytangential relation with the upper or sheet supporting surface I9 of thesupport plate 4. The feed rolls I8 areconnected with the shaft 1 to bedriven therefrom in the direction to feed sheets by means of automaticoverrunning clutches generally designated at 2|.

A speed increasing spur gear transmission serves to drive the shaft Iand consequently the feed rolls I8 from the driven gear I1 and theroller II and comprises, see Figure 3, relatively large and small spurgears 22 and 23 disposed coaxially of the shaft I and respectivelysecured with the driven gear I I and roller II and with the shaft I, anda counter gear member 24 rotatably mounted in parallelism with the shaftI on a stud 25 secured on the bracket 6 and provided with relativelysmall and large spur gears 26 and 21 respectively meshing with the gears22 and 23.

The support plate 4 is adapted to support, on the upper or sheetsupporting surface I9 thereof, a stack of sheets 28 on edge, see Figure1, and a pusher 29 is mounted on the support plate for movementlongitudinally thereof, in a manner unnecessary to be described, and isyieldably urged by gravity, because of the inclination of the supportplate, to advance the stack of sheets facewise against the feed rollsI8. Positioning devices, generally designated at 3|, are mounted on arod 32 extending between and secured to the brackets 5 and 6 above thefeed rolls I8, and extend upwardly from this rod for forward engagementof the front of the sheet stack thereagainst as the pusher 29 advancesthe stack against the feed rolls I8. The feed drum I and drive gear 3rotate clockwise in Figures 1, 4, 5 and 6 and the drive gear rotates thedriven gear IT and the feed rolls I8 counter clockwise in these figuresthrough the transmission 2223-25 25-41 and overrunning clutches 2 I, andthe feed rolls grip and sequentially feed the sheets at the front of thestack edgewise and over the forward portion of the support plate 4, asshown in Figure 4, to the feed drum on which they are gripped bypressure rollers, not shown, and their feeding is thereby continued.

Referring to Figures 1, 6 and '7, a support arm 33, preferably in theform of a stamping, is arranged below the support plate 4 incorrespondence therewith and extends transversely of the axis of theshaft I and feed rolls 8, and is provided with alined'oppositelyextending transverse branches 34 adjacent its forward end. The arm ispivotally mounted on the support plate on an axis parallel to and spacedrearwardly from the feed rolls I8 by means of spaced lugs 35 struckdownwardly from the support plate and upturned outer ends 35 of thebranches 34 respectively pivotally mounted on the lugs 35 as designatedat 31.

Referring particularly to Figure 6, the forward end of the arm 33 isupturned, as designated at 38, and is bored, as designated at 39, on anaxis transverse to the pivotal axis of the arm, and an internallythreaded shouldered bushing 40 is secured in the bore 39. An elongatedcylindrical adjusting member 4! is provided with an axial bore 42, andits relatively small forward portion 43 is externally screwthreaded andscrewthreaded into the bushing 4! for, axial adjustment of the adjustingmember relative to and transversely of the pivotal axis of the arm 33. Aleaf spring 44 is arranged above the arm 33 and hasits rear end securedon the arm and has its front end tensioned against the periphery of therear end of the adjusting member M to retain it in adjusted position.

A bored friction bearing 45, provided with a bearing bushing 46 offriction material such as leather, is arranged forwardly of the arm 33and is provided with a shank 47 extending radially thereof, and thisshank extends through the bore of the bushing 49 of the arm 33 andthrough the bore 42 of the adjusting member 4|, the shank being engagedin the bore 42 for rotation and 1on gitudinal movement and preferablybeing smaller than this bore as shown in Figure 6.

A helical compression spring 48 is arranged in an enlarged rear boreportion 45 of the bore 42 of the adjusting member 4i and encircles theshank 41, and is engaged between a shoulder 50, on the adjusting memberand formed by the enlarged bore portion 49 thereof, and a split springwasher 5I engaged in a circumferential groove 52 on the rear end of theshank, so that the spring 48 urges the shank and with it the frictionbearing 45 rearwardly.

An elongated support 53, see Figures 6 and '7, extends transversely ofthe shank 4'! and is provided with a bore 54 through the intermediateportion thereof and through which the shank extends, this support beingarranged between the bearing 45 and the bushing 48, and the bore 54being preferably larger than the shank 4'1. The end portions of thesupport 53 are turned forwardly and are provided with forwardly facingrecesses 55 as best shown in Figure 8. A shaft 56 is arrangedlongitudinally of the support 53, and bearings 57 are engaged on thisshaft respectively in the regions of the ends thereof and arerespectively rearwardly engaged in the bearing recesses 55. The frictionbearing 45 is disposed intermediate the bearings 51 and the shaft 56extends through and is thus radially engaged by the bearing 45, and thespring 48, reacting on the adjusting member 41 andv through on thesupport arm 33, draws the shank 41 and. with it' the bearing 45rearwardly and thus maintains the bearings 57 engaged in. the hearingrecesses 55", presses the support 53 rearwardly against the bushing 4%}to yieldably position the support with the shaft 56 parallel? to thepivotal axis of the support arm 33, and presses the friction bearing 45radially against the shaft 56 to provide a yieldable friction brake:retardingrotation of this shaft.

Two axially spaced friction retard rolls 59- are secured respectively onopposite :ends of the: shaft 56 for rotation therewith, see:particularly Figure- 7, and each retard; roll comprises a bored metalcore 61 and a rim- 62 of friction material such as soft rubber. Thecore- 6| of each retard roll is engaged on a reduced end 63 onthe shaft56. and is provided at its inner end with a dia metrical slot 66 whichengages across pin 6.5 on the shaft to angularly fix the retard. roll.on the shaft, and a split spring washer $6 is engaged in acircumferentiai grooverfil on the end-of the shaft to retain the retardroll thereon.

A vertically disposed adjusting screw 68' is screwthreade'd downwardlythrough the rear end of the support arm 3-3,.as bestshown in Figure 6,and a lock nut 89 is screwthreaded on: the adjusting screw'belowthe-support arm and is en'-' gageable upwardly thereaga-inst to retainthe adjusting screw in adjusted position. A helical compression. springII is arranged coaxially of.

the screw 68* and in. a blind axial bore 12 of the adjusting screw, andisengaged between the screw and the support plate 4 to urge the rear endof the support arm 33 downwardly and the forward end of this arm and theretard rolls'59 upwardly. v I I To facilitate predetermined adjustmentof the adjusting member t-l, see Figures 6 and 7-, a collar 13 issecured rearwardly on the portion 43 of this member and is providedabout its periphery with a series of indexing numbers M which areobservable through an aperture 1-5 in the support arm 33, and tofacilitate predetermined adjustment of the adjusting. screw 68,see-Figuresrl and 6, a collar it is. secured on this screw and isprovided about its periphery with a series'of-indexing numbers 11.

The retard rolls 59 and shaft- 56' are disposed below and in parallelrelation with the feed rolls to and shaft '1 with the retard rolls inopposing. relation respectively with the feed rolls. for the sequentialfeed of sheets between the feed and retard rolls, and the pivotal axisof the support arm. 33 is disposed parallel to and is horizon: tallyspaced from the retard rolls and shaft 56 so that the retard rolls aremoveable toward and away from the feed rolls. The spring 71 yieldablyurges the retardv rolls toward the feed rolls for pressure engagement ofthe fed. sheets between the feed and retard rolls, and. the spring :28frictionally engages the bearing 45' radially against the shaft 56 toretard rotation. of the retard rolls.

Recalling that the feed drum I rotates clockwise and the feed rolls [8rotate counter clockwise in Figures 1, 4,. 5 and 6,. and referring toFigure 4., the feed rolls I 8- normallygrip and feed each foremost sheet18 of the sheet stack 28 and feed it downwardly and about the feed rollsand over the corresponding end of the support plate a between the feedrolls and the retard rolls 59, and thus sequentially feed the sheetsfrom the sheet stack to the feed drum I on; which they are grippedbypressure rollers, not shown, for the further feeding thereof, the sheetsbeing under pressure between the feed and. retardrollsby reason of thespring H urg ing the retard rolls toward the feed. rolls; single sheetsare fed under pressure between the feed and retardrolls, the retardrolls are rotated clockwise, see. Figure 4,. because while the yield--able friction braking effect of. the bearing 45 on the shaft 56,, abovedescribed, resists rotation of the retard rolls, this resistance isovercome by the friction between the feed rolls and a single sheet andbetween the sheet and the retard rolls, thus promoting the uniformfeeding of single sheets even though they are of random thickness.However, the yieldable. friction ofthe bearing? 45 resistsrotation ofthe retard rolls to an extent sufficient to cause slippage betweensuperposed sheets 18 and 19, see Figure 5, between the feedand retardrolls by stoppage: of the retard. rolls and consequent temporarystoppage of the sheet 19 contacting theretard rolls while the foremostsheet it contacting the feed roll. is fed. After the foremost sheet 18is fed from the feed and retard: rolls, the sheet 19 is feel, afterwhich the feed rolls grip the then foremost sheet of. the sheet stackand feed the same. I

Observing that the pivotal axis of the support 53 on the support arm 33is disposed transversely to the common axial plane of the feed andretardrolls I 8 and 59- and intermediate the retard: rolls or in other wordsintermediate the limits of con.- tact of the retard rolls axiallythereof with sheets fed between the feed and retard rolls, the re.- tardrolls are urged toward the feed rolls by the spring llinpressureequalized relation .and thus act correspondingly on the:sheets fed between the feed and retard rolls to minimize any tendencyof. the sheets to skew While I have thus described my invention, I donot wish to be limited to the precise details described, as changes maybe readily madewithout departing from the spirit of my invention, buthaving thus described my invention, I claim as new and desire to: secureby Letters Patent the following:

1. In an automatic sheet feeding mechanism,

the combination: of. a rotatable driven friction feed rollmeans, aconstantly rotatable friction retard roll means disposed similarly toand: in opposing relationwith said feed roll means for the sequentialfeeding of sheets therebetween, a first support member. mounted formovement corresponding with movement of said retard: roll means towardand away from said feed, roll means, a second support member carryingsaid retard roll means for rotation and pivota-lly mounted onsaid firstsupport member on an axis. transverse to the common axial plane of saidfeed and retard roll means and intermediate the limits of contact ofsaid retard roll meam axially thereof with sheets fed between said feedand retard roll means, resilient means for yieldably urging said firstsupport member in the direction to urge said retard roll means towardsaid feed roll means, and yieldable friction brake, means for. retardingrotation of said'retard r011 means.

2. In an automatic sheet feeding mechanism, the combination of arotatable driven friction feed roll means, a constantly rotatable shaftdisposed in parallelism with said feed roll means, two axially spacedfriction retard rolls mounted on saidv shaft for rotation therewith forthe sequen tial. feed of sheets between said retard rolls andfeed rollmeans, a first support member mounted for movement corresponding withmovement of said retard rolls toward and away from said feed roll means,a second support member pivotally mounted on said first support memberon an axis transverse to the common axial plane of said feed roll meansand shaft and intermediate said retard rolls, two bearings respectivelydisposed in the regions of said retard rolls for carrying said shaft forrotation on said second support member, a yieldable friction brakeengagedwith said shaft between said bearings for retarding rotation ofsaid retard rolls, and resilient means yieldably urging said firstsupport member in the direction to urge said retard rolls toward saidfeed roll means.

3. In an automatic sheet feeding mechanism, the combination of arotatable driven friction feed roll means, a constantly rotatable shaftdisposed in parallelism with said feed roll means, two axially spacedfriction retard rolls mounted on said shaft for rotation therewith forthe sequential feed of sheets between said retard rolls and feed rollmeans, a first support member mounted for movement correspondingwith'movement of said retard rolls toward and away from said feed rollmeans, a second support member pivotally mounted on said first supportmember on an axis transverse to the common axial plane of said feed rollmeans and shaft, and intermediate-said retard rolls, mean carrying saidshaft for rotation on said second support member comprising two bearingsrespectively disposed in the regions of said retard rolls, a frictionmember engaged radially with said shaft between said two bearings,pressure means pressing said friction member radially against said shaftfor yieldably retarding rotation of said retard rolls, and resilientmeans for yieldably urging said first support member in the direction tourge said retard rolls toward said feed means.

4. In an automatic sheet feeding mechanism, the combination of arotatable driven friction feed roll means, a constantly rotatable shaftdisposed in parallelism with said feed roll means,

two axially spaced friction retard rolls mounted on said shaft forrotation therewith for the sequential feed of sheets between said retardrolls and feed roll means, a first support member mounted for movementcorresponding with movement of said retard rolls toward and away fromsaid feed roll means, a second support member pivotally mounted on saidfirst support member on an axis transverse to the common axial plane ofsaid feed roll means and shaft and intermediate said retard rolls, twobearings respectively disposed in the regions of said retard rolls forcarrying said shaft for rotation on said second support member, afriction member engaged radially on said shaft intermediate said twobearings, resilient means pressing said friction member radially againstsaid shaft for yieldably retarding rotation of said retard rolls andcomprising a shank on and extending radially of said friction member incoaxial relation with the pivotal axis of said second support member,and resilient means for yieldably urging said first support member inthe direction to urge said retard rolls toward said feed roll means.

5. In an automatic sheet feeding mechanism, the combination of claim 4and further comprising the pivotal mounting of said second supportmember on said first support member comprising apertures through saidfirst and second support members and'said shank extending through saidapertures.

' 6. In an :automatic sheet feeding mechanism, the combination of claim4 and further comprising said first mentioned resilient means and thepivotal mounting of said second support member on said first supportmember comprising apertures through said first and second supportmembers, said shank extending through said apertures, and a. helicalspring encircling said shank.

7. In an automatic sheet feeding mechanism, the combination of claim 4and further comprising said first mentioned resilient means and thepivotal mounting of said second support member on said first supportmember comprising apertures through said first and second supportmembers, an adjusting member screw-threaded into the aperture of one ofsaid support members and provided with an axial bore, said shankextending through said apertures and bore, and

a helical spring encircling said shank and operative between saidadjusting member and shank.

8. In an automatic sheet feeding mechanism, the combination of arotatable driven friction feed roll means, a constantly rotatable shaftdisposed in parallelism with said feed roll means, two axially spacedfriction retard rolls mounted on said shaft for rotation therewith forthe sequential feed of sheets between said retard rolls and feed rollmeans, a first support member mounted for movement corresponding withmovement of said retard rolls toward and away from said feed roll means,a second support member pivotally mounted on said first support memberon an axis transverse to the common axial plane of said feed roll meansand shaft and intermediate said retard rolls and provided with twobearing receiving recesses respectively in the regions of said retardrolls and facing said shaft, two bearings on said shaft and respectivelydisposed in the regions of said retard rolls and engaged in said bearingrecesses for carrying said shaft for rotation on said second supportmember, a friction bearing engaged radially on said shaft intermediatesaid two bearings, resilient means pressing said friction bearing memberradially against said shaft in the direction opposite that in which saidbearing recesses face for maintaining said two bearings in engagementwith said bearing recesses and for yieldably retarding rotation of saidretard rolls and comprising a shank on and extending radially of saidfriction bearing in coaxial relation with the pivotal axis of saidsecond support member and a helical spring surrounding said shank, and

resilient means yieldably urging said first support member in thedirection to urge said retard rolls toward said feed roll means.

9. In an automatic sheet feeding mechanism, the combination of claim 8and further comprising said first mentioned resilient means and thepivotal mounting of said second support member on said first supportmember comprising apertures through said first and second supportmembers, an adjusting member screw-threaded into the aperture of saidfirst support member and provided with an axial bore, said shankextending through said apertures and bore, and a helical compressionspring encirclin said shank and operative between said adjusting memberand shank.

10. In an automatic sheet feeding mechanism, the combination of stacksupporting and advancing means comprising a stack support plate forsupporting a stack of sheets on edge, a rotatable driven friction feedroll means arranged transversely of and above and in approximatelytangential relation with the sheet supporting surface of said supportplate and against which the sheet stack is facewise advanced, aconstantly rotatable retard roll means disposed below and similarly toand in opposing relation with said feed roll means for the sequentialfeeding of sheets therebetween from said stack, a first support memberarranged below said support plate and pivotally mounted thereon formovement on an axis parallel to and horizontally spaced from the axis ofsaid retard roll means, a second sup-- port member arranged below saidsupport plate and carrying said retard roll means for rotation andpivotally mounted on said first support member on an axis transverse tothe common axial plane of said feed and retard roll means andintermediate the limits of contact of said retard roll means axiallythereof with sheets fed between said feed and retard roll means,resilient means operative between said support plate and first supportmember for yieldably urging said first support member in the directionto urge said retard roll means toward said feed roll means, andyieldable friction brake means for retarding rotation of said retardroll means.

11. In an automatic sheet feeding mechanism,

I the combination of claim and further comprising said resilient meanscomprising an adjusting member screwthreaded on said first supportmember on an axis spaced from and transverse to the pivotal axis of saidfirst support member and a helical compression spring arranged coaxiallyof said adjusting member and engaged between said support plate andadjusting member.

12. In an automatic sheet feeding mechanism, the combination of stacksupporting and advancing means comprising a stack support plate forsupporting a stock of sheets on edge, a rotatable driven friction feedroll means arranged transversely of and above and in approximatelytangential relation with the sheet supporting surface of said supportplate and against which the sheet stack is facewise advanced, aconstantly rotatable shaft disposed below and in parallelism with saidfeed roll means, two axially spaced friction retard rolls mounted onsaid shaft for rotation therewith for the sequential feeding of sheetsbetween said retard rolls and feed roll means, a first support memberarranged below said support plate and pivotally mounted thereon formovement on an axis parallel to and horizontally spaced from the axis ofsaid retard roll means, a second support member arranged below saidsupport plate and pivotally mounted on said first support member on anaxis transverse to the common axial plane of said feed roll means andshaft and intermediate said retard rolls, two bearings respectivelydisposed in the regions of said retard rolls for carrying said shaft forrotation on said second support member, a friction member engagedradially on said shaft intermediate said two bearings, resilient meanspressing said friction member radially against said shaft for yieldablyretarding rotation of said retard rolls and comprising a shank on andextending radially of said friction member in coaxial relation with thepivotal axis of said second support member, and resilient meansoperative between said support plate and first support member foryieldably urgin said first support member in the direction to urge saidretard rolls toward said feed roll means.

13. In an automatic sheet feeding mechanism, the combination of claim 12and further comprising the pivotal mounting of said second supportmember on said first support member comprising apertures through saidfirst and second support members and said shank extending through saidapertures.

14. In an automatic sheet feeding mechanism, the combination of claim 12and further com prising said first mentioned resilient means and thepivotal mounting of said second support member on said first supportmember comprising aper-- tures through said first and second supportmembers, an adjusting member screw-threaded into the aperture of saidfirst support member and provided with an axial bore, said shankextending through said apertures and bore, and a helical compressionspring encircling said shank and operative between said adjusting memberand shank, and said second mentioned resilient means comprising anadjusting member screwthreaded on said first support member on an axisspaced from and transverse to the pivotal axis of said first supportmember and a helical compression spring arranged coaxially of said lastmentioned adjusting member and engaged between said support plate andlast mentioned adjusting member.

ELMER L. JOHNSON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,089,946 Davidson Aug. 17, 1937 2,224,138 Trydal Dec. 10,1940 2,359,856 Morse Oct. 10, 1944

